An eye-tracked head-mounted display (ET-HMD) system is able to display virtual images as a classical HMD does,
while additionally tracking the gaze direction of the user. There is ample evidence that a fully-integrated ETHMD
system offers multi-fold benefits, not only to fundamental scientific research but also to emerging
applications of such technology. For instance eyetracking capability in HMDs adds a very valuable tool and
objective metric for scientists to quantitatively assess user interaction with 3D environments and investigate
the effectiveness of various 3D visualization technologies for various specific tasks including training,
education, and augmented cognition tasks. In this paper, we present an innovative optical approach to the
design of an optical see-through ET-HMD system based on freeform optical technology and an innovative
optical scheme that uniquely combines the display optics with the eye imaging optics. A preliminary design
of the described ET-HMD system will be presented.